Alk rising without dosing

[Tamberav]

Hello, trying to wrap my head around why Alk steadily increases every week without any dosing (no pH additives either).

22g AIO
5g water change every week - source water is Fritz salt, Alk is steady 8.7 every test/batch.
Cheato in back chamber, filter floss + BRS Rox Carbon and Purigen in media bag (plan on removing the purigen today, need more nutrients).
No skimmer, no GFO (had them but both removed May 13th).
Light is 4 t5 bulbs + 4 nano-box pucks hung about 2 ft up since it is overkill.
5 fish fed LRS frozen food 1-2 times per day
Handful of small SPS frags that are very slowly growing
Tank is 1 year old

Alk after last water change was 9.2 on May 18th, tested alk just now before water change, it is 9.8 (I checked it twice).
Salinity 1.026 with calibrated refractometer (double checked with a 2nd one)
Calcium 445 (red sea)
Mg 1380 (red sea)
Po4 0 (hanna low range phosphorous, usually runs 0.02)
Nitrate: 0.50 (red sea)
Temp: 76 (Noticed today I did have some swings at night down to 72, yikes, bad heater, replacing it today)

I use hanna alk checker, bought a new reagent, same results. I also bought the hanna alk standard set and it verified the hanna was working correctly.

Top off water is RODI using Spectrapure unit, 0 TDS, filters changed a few months ago. ATO container is a food safe water container, water from inside ATO tests 0 for ALK.

Sand is tropic eden dry reef flakes

Rock is Reef-Cleaners dry rock that has been with me live/kept wet for several years now in various tanks.

Let me know if I missed anything.

Thank you.

 

[Crabs McJones]

Hello, trying to wrap my head around why Alk steadily increases every week without any dosing (no pH additives either).

22g AIO
5g water change every week - source water is Fritz salt, Alk is steady 8.7 every test/batch.
Cheato in back chamber, filter floss + BRS Rox Carbon and Purigen in media bag (plan on removing the purigen today, need more nutrients).
No skimmer, no GFO (had them but both removed May 13th).
Light is 4 t5 bulbs + 4 nano-box pucks hung about 2 ft up since it is overkill.
5 fish fed LRS frozen food 1-2 times per day
Handful of small SPS frags that are very slowly growing
Tank is 1 year old

Alk after last water change was 9.2 on May 18th, tested alk just now before water change, it is 9.8 (I checked it twice).
Salinity 1.026 with calibrated refractometer (double checked with a 2nd one)
Calcium 445 (red sea)
Mg 1380 (red sea)
Po4 0 (hanna low range phosphorous, usually runs 0.02)
Nitrate: 0.50 (red sea)
Temp: 76 (Noticed today I did have some swings at night down to 72, yikes, bad heater, replacing it today)

I use hanna alk checker, bought a new reagent, same results. I also bought the hanna alk standard set and it verified the hanna was working correctly.

Top off water is RODI using Spectrapure unit, 0 TDS, filters changed a few months ago. ATO container is a food safe water container, water from inside ATO tests 0 for ALK.

Sand is tropic eden dry reef flakes

Rock is Reef-Cleaners dry rock that has been with me live/kept wet for several years now in various tanks.

Let me know if I missed anything.

Thank you.

My guess is that by doing 5 gallon water changes on a 22 gallon tank a week, you're replenishing nutrients faster than your corals are consuming it.

 

[Tamberav]

That would make sense but my freshly mixed salt water is only 8.7 alk while my tank is 9.8. A water change brings me down to roughly 9.2 and then it increases again by the end of the week.

 

[Reefing Madness]

What kind of rock you have in the tank?

 

[Randy Holmes-Farley Verified Community Expert]

I’d keep watching to see if there is a longer trend than 2 measurements.

That said, declining nitrate can boost alkalinity.

Any other additives at all?


I’m not sure what might be in the foods you use, but some ingredients such as vitamin C in the sodium form, can boost alk.

 

[Tamberav]

Reef-cleaners rock.

I will keep testing.

I have never had high Nitrates... usually 0 but finally got some readings these last few weeks. I am trying to get them higher. I had a small PO4 spike on May 10th from feeding too much flake (stopped that too, just LRS since, maybe a few pellets now and again). Added some GFO, when PO4 hit 0.02 3 days later, I pulled out the GFO and added the cheato.

Here is a snap of the tanks history, most of the Alk readings were AFTER a water change. I noticed the alk problem on March 21st, salt mix was 7.9 but tank was 9.4. I had been using some Acro Power, so I stopped. That was 2 months ago.

Since those 2 months it has only been water changes + LRS fish food and pellets (rarely). Nothing else, was trying to weed out the problem.

 

[Randy Holmes-Farley Verified Community Expert]

With no apparent additives that have alk, the usual suspects are top off water and artificial rock/cement that wasn't fully cured.

That said, it is not hard to drop alk a bit if it becomes an ongoing issue.

 

[Tamberav]

Nothing like that in the tank, top off is RODI and alk tests 0. No artificial rock...hmmm.. LRS food does have vit C in it but not sure how much it would take. Will just keep testing, really puzzling!

 

[Randy Holmes-Farley Verified Community Expert]

Nothing like that in the tank, top off is RODI and alk tests 0. No artificial rock...hmmm.. LRS food does have vit C in it but not sure how much it would take. Will just keep testing, really puzzling!

If it gets too high, let us know and we can advise on how to lower it.